Contact microscopy is known. Typically, x-rays are directed onto a sample placed on an x-ray sensitive medium. The x-rays may be continuous or pulsed with nanosecond duration and high intensity and are recorded on the medium. Thereafter, the medium is developed and the x-ray shadow image is examined with an electron microscope. Excellent image contrast results. See Synchrontron Radiation published by Plenum Press of New York, N.Y. 1980, pp. 277-322.
No continuous imaging for observing specimens in vivo is usually possible. A single picture of the specimen is all that is provided. Stereoscopic imaging with depth information is also not easily obtained as specimen must be lifted off medium and redeposited on new medium for multiple exposures.
It is also known to construct a photoelectron x-ray microscope on a flat surface. X-rays bombard the flat surface through a sample and thereafter liberate electrons from a semitransparent photocathode. This contact method of producing an electron image requires electron optics to image the electrons. These optics are expensive and complex.
Point source x-ray projection microscopes are known. A point source of x-rays projects an enlarged shadow of a sample onto a distant image plane. This method has limitations in that image resolution is lost due to finite x-ray source size--a point source is never truly produced. Further there is a need to have the object very close to the x-ray source, which is a practical limitation.
Field ion and field emission microscopy is known. The sample is the tip of a very sharp needle. A high electric field is generated at the needle point causing electrons or ions to flow radially from the needle to a distant screen producing an enlarged image. High magnification with 2 to 3 .ANG. resolution in the ion case results. See Field Ion Microscopy published by AMERICAN ELSEVIER 1969. Unfortunately using this technique, there has been little success in examining biological samples placed on the surface of the needle. Images of atomic structure on the exterior surface of the needle can only be produced. Since the needle must be exposed to a vacuum, in vivo examination of the specimen is again not possible even if the other problems were solvable.
Scanning x-ray microscopes are known. In such technique a collimated x-ray beam is scanned in a raster pattern. An image is created by mapping the point to point intensity of the transmitted beam. Unfortunately, in this technique, the limitations include the size of the beam that one is able to produce. Consequently, the resolution of the image is limited to the beam diameter.
Microscopes using focusing elements for x-rays are known. These use grazing incidence optics or zone plate focusing techniques on the x-rays. Unfortunately in such microscopes, the x-rays are poorly focused by presently available optics.
Electron microscopes are known. In such microscopes samples are cut to extremely thin sections. Unfortunately, the contrast of such thin section material when bombarded by electrons is not good. Therefore, stains are frequently required in use. Moreover, the sample is placed in a vacuum chamber for observation. Therefore, in vivo observation of the sample is not possible.